In the alveoli of the lung the surface tension at the air-liquid interface is lowered by the presence of a lipoprotein complex called pulmonary surfactant. The importance of pulmonary surfactant becomes evident in the prematurely born infants deficient in this lipoprotein complex who manifect respiratory distress syndrome (RDS). Studies suggest that surfactant proteins may have an important functional role in the lung by enhancing the rate of surfactant adsorption and spreading movement from the hypophase of aqueous solutions. To better understand the role of the surfactant-associated proteins in the function of pulmonary surfactant, it is of obvious importance to study the regulation and physiology of these proteins. To address these questions, ones approach is to develop specific probes for these proteins. We propose to prepare a complementary DNA (cDNA) expression bank in Lambdagt11 vector from human lung mRNA. We will screen the bank with a specific antiserum that recognizes the primary translation products of the surfactant proteins that is available in our laboratory. With this screening we will be able to identify cDNA clones for mRNAs encoding surfactant-associated proteins. Subsequently we plan to use these positive cDNA clones as probes to identify the molecular components of these proteins (i.e. the number and size of mRNA sequences coding for these proteins). In addition we will obtain cDNA probes specific for each mRNA coding for these proteins, which will be useful to carry out regulatory studies for each molecular component of these proteins. The availability of such probes will also permit a) structural studies of the gene(s) of these proteins that may provide a specific indicator for prenatal diagnosis of RDS b) regulatory studies of the expression of these proteins under normal and disease conditions c) in vivo and in vitro functional studies to better understand the role of these proteins in the function to surfactant and possibly therapeutic studies.